			Home About us Contact

Coat Colour Pattern (coat + colour_pattern)

Distribution by Scientific Domains

Life Sciences	75%

Selected Abstracts

Genetic mapping of dominant white (W), a homozygous lethal condition in the horse (Equus caballus)

JOURNAL OF ANIMAL BREEDING AND GENETICS, Issue 6 2004
C. Mau
Summary Dominant white coat colour (W) is a depigmentation syndrome, known in miscellaneous species. When homozygous in the horse (similar in mice), the mutation responsible for the white phenotype is lethal in a very early stage of gestation. It seems, that the action of the dominant white allele is not always fully penetrant, resulting occasionally in spotted look alike offspring. These horses resemble a coat colour pattern known as sabino spotting. So far, it is not known whether dominant white (W) and sabino spotting (S) share a common genetic background. In this study, a pedigree consisting of 87 horses segregating for dominant white (W) was used to genetically localize the horse (W)-locus. Microsatellite ASB23 was found linked to (W), which allowed us to map dominant white to a region on horse chromosome 3q22. Tyrosine kinase receptor (KIT) was previously mapped to this same chromosome region (3q21,22). KIT and its ligand (KITLG) are responsible for the normal function of melanogenesis, haematopoiesis and gametogenesis. So far, sequence analysis of different KIT gene fragments did not lead to new polymorphisms, except for a SNP detected in KIT intron 3 (KITSNPIn3). Additional microsatellites from ECA3q (TKY353 and LEX7), together with KITSNPIn3 allowed us to state more precisely the (W)-mutation. The positional results and comparative functional data strongly suggest that KIT encodes for the horse (W)-locus. Zusammenfassung Die dominant weisse Fellfarbe (W) ist eine Form der Depigmentierung, die bei vielen Spezies auftritt. Beim Pferd wirkt die Mutation für Dominant Weiss (W) in homozygoter Form (analog zur Maus), bereits in einem sehr frühen Stadium der Trächtigkeit letal. Es scheint, dass die Wirkung des dominant weissen Allels nicht immer mit vollständiger Penetranz erfolgt. Dies führt gelegentlich zu Nachkommen mit einer Art Schecken-Fellzeichnung. Solche Pferde sind phänotypisch mit den sogenannten ,,Sabino-Schecken,, vergleichbar. Es ist bis jetzt nicht bekannt ob Dominant Weiss (W) und Sabino-Scheckung (S) einen gemeinsamen genetischen Hintergrund besitzen. Mittels eines Pedigrees aus 87 Pferden, in dem Dominant Weiss (W) segregiert, konnte in der vorliegenden Studie der equine (W)-Locus genetisch lokalisiert werden. Der Mikrosatellit ASB23 erwies sich als gekoppelt mit (W) und ermöglichte die Zuweisung des (W)-Locus auf eine Region von Chromosom ECA 3q22. Das Gen für den Tyrosinkinaserezeptor (KIT) liegt ebenfalls in dieser Chromosomenregion (3q21,22). Das KIT -Gen ist zusammen mit dem KIT -Liganden (KITLG) verantwortlich für einen normal funktionierenden Ablauf der Melanogenese, Hämatopoese und Gametogenese. Die direkte Sequenzierung von KIT -Genfragmenten führte bis jetzt zu keinen neuen Polymorphismen, ausser einem SNP in KIT Intron 3 (KITSNPIn3). Mittels weiterer Mikrosatelliten von ECA3q (TKY353 and LEX7) sowie KITSNPIn3 gelang es, die (W)-Mutation genauer zu positionieren. Die vorliegenden Lokalisierungsresultate und vergleichende funktionelle Erkenntnisse deuten stark darauf hin, dass KIT für den Pferde (W)-Locus kodiert. [source]

Backcross breeding for improved resistance to common bacterial blight in pinto bean (Phaseolus vulgaris L.)

PLANT BREEDING, Issue 3 2005
N. Mutlu
Abstract Common bacterial blight (CBB) caused by Xanthomonas campestris pv. phaseoli reduces common bean (Phaseolus vulgaris L.) yield and quality worldwide. Genetic resistance provides effective disease control; however. a high level of resistance is difficult to attain and does not exist in pinto bean, the most important dry bean market class in North America. Our objective was to determine if a backcross breeding approach with the aid of molecular markers linked to quantitative trait loci (QTL) for resistance to CBB in a donor parent could be used to attain higher levels of resistance to CBB in pinto bean. QTL conditioning CBB resistance from the donor parent XAN 159 were introgressed into the recurrent parent,Chase'using classical backcross breeding and intermittent marker-assisted selection.,Chase'pinto bean is moderately resistant and the breeding line XAN 159 is highly resistant to Xanthomonas campestris. Marker assays confirmed the presence of independent QTL from GN no. 1 Sel 27 and XAN 159 in advanced backcross-derived pinto bean lines with improved CBB resistance. Agronomic characteristics of,Chase'were fully recovered in the backcross-derived lines. An important QTL for CBB resistance from XAN 159 on linkage group B6 was not introgressed because tight linkage between this QTL and the dominant V allele that causes an unacceptable black-mottled seed coat colour pattern in pinto bean could not be broken. [source]

Differences in the expression of the ASIP gene are involved in the recessive black coat colour pattern in sheep: evidence from the rare Xalda sheep breed

ANIMAL GENETICS, Issue 3 2008
L. J. Royo
Summary Here we have tested the hypothesis of association between different levels of agouti signalling peptide (ASIP) mRNA and the recessive black coat colour in the rare Xalda breed of sheep. To deal with this task, we first tested the possible action of both the dominant black extension allele (ED) and a 5-bp deletion (X99692:c.100_104del; Adel) in the ovine ASIP coding sequence on the black coat colour pattern in 188 Xalda individuals. The ED allele was not present in the sample and only 11 individuals were homozygous for the AdelASIP allele. All Xalda individuals carrying the Adel/Adel genotype were phenotypically black. However, most black-coated individuals (109 out of 120) were not homozygous for the 5-bp deletion, thus rejecting the Adel/Adel genotype as the sole cause of recessive black coat colour in sheep. Differences in expression of ASIP mRNA were assessed via RT-PCR in 14 black-coated and 10 white-coated Xalda individuals showing different ASIP genotypes (Awt/Awt, Awt/Adel and Adel/Adel). Levels of expression in black animals were significantly (P < 0.0001) lower than those assessed for white-coated individuals. However, the ASIP genotype did not influence the ASIP mRNA level of expression. The consistency of these findings with those recently reported in humans is discussed, and the need to isolate the promoter region of ovine ASIP to obtain further evidence for a role of ASIP in recessive black ovine pigmentation is pointed out. [source]